The present invention relates to a boom truck adapted for handling a unitary load, such as a container and the like, both above as well as below ground level, comprising                an elongated chassis having                    a front end, and            a rear end,                        a front pair of wheels,        a rear pair of wheels,        a telescopic lifting boom having                    a base portion with a rear end and a front end, and            a telescopic arm defining the front end of the lifting boom, wherein the lifting boom is            pivotally mounted for pivoting in a vertical plane and extends above the chassis and past the front pair of wheels of the chassis,                        a lifting unit, which is arranged in connection to the front end of the lifting boom and is separated by a space from the front end of the chassis, as seen in the starting position of the lifting boom, for carrying the unitary load,        a support structure for supporting the lifting boom, said support structure comprising                    a first support arranged on the chassis at the rear portion thereof, for extending in a direction upwards.                        
The expression “container” refers to a transport container for goods, intended for repeated use and designed so that it can be handled and moved as a unit without reloading of the goods. By using standardized container sizes and specially adapted transporting means and handling equipments, containers with goods can be transported quickly and safely from e.g. a manufacturing company to a customer. The containers which can be handled by the boom truck according to the present invention are very heavy and can weigh up to 45 tons, with goods.
U.S. Pat. No. 6,024,232 describes a boom truck having a support structure for supporting a telescopic lifting boom, said support structure consisting of only one stand which is pivotally journalled to the chassis and the lifting boom to enable raising and lowering of the lifting boom from a horizontal, lower transport position, to a horizontal, upper working position. The previously known boom truck cannot perform handling of unitary loads, such as containers, to and from levels below the supporting plane of the boom truck, so called negative lifts.
U.S. Pat. No. 4,964,778 describes a forklift truck having a boom structure consisting of a main boom and an auxiliary boom, which are articulately connected to each other via a knee-joint resembling fly section in order to enable handling of loads below the ground level. The purpose of the forklift truck is to achieve high heights and long reach in front of the truck, above and below the ground level, with its two-part boom design. The design and mounting to the chassis of the boom structure should be sufficient for handling such light loads which can be carried by its fork. However, the forklift truck according to this document is not suited for handling of heavy loads, weighing over 4 tons, since the design and mounting of the boom structure result in instability when handling heavier loads, which instability can lead to increased harmful stresses on the boom structure and which can also produce undesired oscillating movements of the heavy load with accompanying increase of said stresses. Accordingly, it is not possible to replace the fork of the forklift truck according to U.S. Pat. No. 4,964,778 with a lifting yoke for handling of containers of the type of standardized goods containers which are used for smooth transport of goods with e.g. special container ships and handling in container terminals, which containers can weigh up to 45 tons, with goods.